Modification of vinyl ester resins with reactive liquid polymers

ABSTRACT

Vinyl ester resins of the type already having reactive liquid polymers reacted into the backbone of the resins, are cured in the presence of a reactive liquid polymer additive admixed with the prereacted vinyl ester resin. Heating of the system during cure causes the reactive liquid polymer additive to miscibilize with the vinyl ester base resin. The vinyl ester resin modified in the manner described above shows a significant enhancement in toughness as measured by fracture energy over unmodified counterparts or counterparts modified by known methods of adduction or admixing alone.

CROSS REFERENCE

This application is a continuation-in-part of U.S. patent applicationSer. No. 07/515,793, now U.S. Pat. No. 5,053,496 filed Apr. 27, 1990,for "Low Viscosity Statistical Monofunctional Carboxylic-Terminated,Amine-Terminated, or Epoxy-Terminated Reactive Liquid Rubber Polymers,and a Process For Preparation Thereof."

FIELD OF THE INVENTION

The invention relates to the modification of vinyl ester resins, and inparticular to the modification of prereacted vinyl ester base resinswith reactive liquid polymers. More particularly, the invention relatesto the modification of vinyl ester base resins, which already havereactive liquid polymers reacted into their backbones, by admixingreactive liquid polymer additives with the prereacted vinyl ester resinand curing the resin in the presence of heat. It is to be understoodthat use of the term "additive" in connection with reactive liquidpolymers herein refers to reactive liquid polymers capable of reactingdue to their statistical functionality or reactive end groups, but whichare admixed or added to the prereacted vinyl ester resins in anunreacted or free state, and which upon curing of the base resins in thepresence of heat physically associate or affiliate with the reactiveliquid polymers already reacted into the backbones of the base resins toform the modified vinyl ester resin of the present invention.

BACKGROUND

Heretofore, in general, there have been two known methods for modifyingor toughening thermoset resins with reactive liquid polymers(hereinafter RLPs) to improve properties such as fracture energy(G_(Ic)) and impact strength without adversely affecting thethermomechanical property retention of the resins. This reaction can beaccomplished by modifying the epoxy resin end group so that the polymerproduct can participate in the thermoset cure. The first prior artmethod is the adduction or reaction of carboxyl-terminatedbutadiene-acrylonitrile type copolymers with epoxy resins. This reactioncan be accomplished by modifying the epoxy resin end group so that thepolymer product can participate in the thermoset cure. Such adductedsystems can be cured in a conventional manner to give elastomer orrubber-modified thermoset resin systems having a significant enhancementin toughness, as measured by fracture energy, over their unmodifiedcounterparts.

A second prior art method of modifying thermoset resins is by admixing aRLP into the resin. Although generally any RLP product can be mixed intoany thermoset resin to give a modified thermoset resin system having thecharacteristic enhanced toughness, such a combination generally is notmiscible. Such lack of miscibility between the RLP and the thermosetresin results in the necessity to thoroughly mix the composition priorto use, which is inconvenient and impractical for most applications.

Although thermoset resins modified by either of the two prior artmethods described above display improved toughness over their unmodifiedcounterparts, thus making them suitable for use in certain applications,such modified thermoset resins still are unsuitable for use in manyapplications where an even greater level of toughness is required.

U.S. Pat. No. 3,892,819 to Najvar relates to vinyl ester resins withimproved impact resistance obtained by a process modification wherein upto 20 percent of the unsaturated monocarboxylic acid, which is reactedwith a polyepoxide, is replaced by an equivalent amount of a liquidcarboxyl terminated polydiene rubber capable of reacting with epoxygroups to form a chemically bound molecule.

U.S. Pat. No. 3,928,491 to Waters relates to a flexible crack-resistantand chemically resistant thermosetting vinyl ester resin which isproduced by coreacting an epoxy resin, a carboxyl terminated elastomerand an unsaturated monocarboxylic acid, such as acrylic or methacrylicacid. The neat resin is miscible and copolymerizable with ethylenicallyunsaturated monomers such as styrene. A novel cast pipe utilizes theresin of the invention as an unreinforced crack-resistant inner lining.

SUMMARY OF THE INVENTION

Objects of the present invention include producing a modified vinylester resin composition having improved fracture energy toughness whileretaining other properties including thermomechanical properties, byadmixing and miscibilizing a reactive liquid polymer additive with avinyl ester resin already having a reactive liquid polymer reacted intothe backbone of the resin composition.

Another object of the present invention includes providing a method forcontrolling the morphology of the modified vinyl ester resincomposition.

A further object of the present invention includes providing such amodified vinyl ester resin composition, wherein the resin compositiongenerally includes the same concentration of RLP or total rubber contentas that present in prior modified vinyl ester resin systems.

These objects are obtained by the vinyl ester resin composition of thepresent invention, comprising, a generally uniformly dispersed admixtureof a prereacted vinyl ester base resin having a reactive liquid polymerreacted into its backbone, and an effective amount of a reactive liquidpolymer additive to improve the fracture energy of the vinyl ester resincomposition.

These objects are further obtained by the method of toughening vinylester resins with reactive liquid polymers of the present invention,wherein the method comprises the steps of, admixing a reactive liquidpolymer additive with a prereacted vinyl ester base resin having areactive liquid polymer reacted into its backbone, and curing theadmixture.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the fracture energy of two different vinylester resins and blends thereof, plotted against the total rubbercontent of the resins and resin blends, including the amount ofepoxy-terminated butadiene-acrylonitrile type copolymer additivecontaining 17 percent bound acrylonitrile admixed with the resins;

FIG. 2 is a graph showing the fracture energy of two different vinylester resins, plotted against the total rubber content of the resins,including the amount of epoxy-terminated butadiene-acrylonitrile typecopolymer additive containing 26 percent bound acrylonitrile admixedwith the resins;

FIG. 3 is a graph showing the fracture energy of two different vinylester resins, plotted against the total rubber content of the resins,including the amount of vinylidine-terminated butadiene-acrylonitriletype copolymer additive containing 20 percent bound acrylonitrileadmixed with the resins;

FIG. 4 is a graph showing the fracture energy of two different vinylester resins, plotted against the total rubber content of the resins,including the amount of hydroxyl-terminated epihalohydrin type polymeradditive admixed with the resins;

FIG. 5 is a stained transmission electron microscopy micrograph ofDerakane 8084 (Derakane being a registered trademark of the Dow ChemicalCompany of Midland, Mich.), magnified 66,800 times;

FIG. 6 is a scanning electron microscopy micrograph of 20 percent byweight of epoxy-terminated butadiene-acrylonitrile type copolymeradditive containing 17 percent bound acrylonitrile, admixed withDerakane 411 and magnified 300 times;

FIG. 7 is a scanning electron microscopy micrograph of 5 percent byweight of epoxy-terminated butadiene-acrylonitrile type copolymeradditive containing 17 percent bound acrylonitrile, admixed withDerakane 8084 and magnified 300 times.

DETAILED DESCRIPTION

The present invention relates to the production of modified vinyl esterresins having unexpectedly improved toughness as measured by fractureenergy, through the admixing of RLP additives with vinyl ester baseresins which already have RLP reacted into their backbones, withoutaffecting thermomechanical property retention of the vinyl ester resins.The method of the present invention enables the morphology of themodified vinyl ester resins to be controlled, and achieves such improvedfracture energies utilizing generally the same total elastomer contentor concentration of RLPS as utilized in prior art methods ofmodification utilizing either the adduction or admixture methods alone.The present invention achieves miscibility of the RLP additive with theprereacted vinyl ester base resin preferably by admixing the RLPadditive with the base resin and subsequently curing the vinyl esterresin system in the presence of heat. However, it is understood that theRLP additive could be admixed with the base resin during cure of theresin and in the presence of heat.

The prereacted vinyl ester resins utilized as a starting material in thepresent invention are formed in the following manner. Generally, aselected epoxy resin is brought together and reacted with apolyfunctional carboxyl-terminated RLP and an unsaturated monocarboxylicacid, wherein the polyfunctional carboxyl-terminated RLP has afunctionality of from about 0.8 to about 3.5. More particularly, theprereacted vinyl ester base resin preferably is formed by reacting anexcess of the selected epoxy resin with a statistically difunctionalcarboxyl-terminated RLP and an unsaturated monocarboxylic acid, whereinthe statistically difunctional carboxyl-terminated RLP has afunctionality of from about 1.7 to about 2.4. It is understood thatother RLPs can be utilized for reacting with the epoxy resin and theunsaturated monocarboxylic acid, including but not limited to, RLPshaving carboxyl functional groups substituted along the backbone of theRLP rather than on the ends thereof.

In general, an epoxy resin is a compound containing more than one α or1,2-epoxy group which is designated by the structural formula: ##STR1##and which is capable of being converted to a useful thermoset or curedstate by an amine curing agent as discussed hereinbelow, whether suchα-epoxy group is situated internally, terminally, or on cyclicstructures.

Epoxy resins which are suitable for use in the present invention includemany commercially available epoxy resins and preferably diepoxy resinswhich are well-known to the art and to the literature. Desirable epoxyresins include polyhydric phenol polyether alcohols; glycidyl ethers ofnovolac resins such as epoxylated phenol-formaldehyde novolac resin;glycidyl ethers of mononuclear di- and trihydric phenols; glycidylethers of bisphenols such as diglycidyl ether of tetrabromobisphenol A;glycidyl ethers of polynuclear phenols; epoxy resin from diphenolicacid; glycidyl ethers of aliphatic polyols such as chlorine-containingaliphatic diepoxy and polyepichlorohydrin; glycidyl esters such asaliphatic diacid glycidyl esters and epoxidized phenolphthalein;glycidyl epoxies containing nitrogen such as glycidyl amides andamide-containing epoxies; glycidyl derivatives of cyanuric acid;glycidyl resins from melamines; glycidyl amines such as triglycidylether amine of p-aminophenol andbis(2,3-epoxypropyl)methylpropylammonium p-toluenesulfonate; andglycidyl triazines; thioglycidyl resins such as epoxidized bisulfide;silicon-glycidyl resins such as1,4-bis[(2,3-epoxypropoxy)dimethylsilyl]; fluorine glycidyl resins;epoxy resins which are synthesized from monoepoxies other thanepihalohydrins including epoxy resins from unsaturated monoepoxies suchas polyallyl glycidyl ether and glycidyl sorbate dimer; epoxy resinsfrom monoepoxy alcohols; epoxy resins from monoepoxies by esterinterchange; epoxy resins from glycidaldehyde; polyglycidyl compoundscontaining unsaturation such as allyl-substituted diglycidyl ether ofbisphenol A; epoxy resins which are synthesized from olefins andchloroacetyls such as butadiene dioxide, vinylcyclohexene dioxide,epoxidized polybutadiene, and bis(2,3-epoxycyclopentyl)ether; andepoxy-resin adducts of the above. A more comprehensive list of epoxyresins can be found in Handbook of Epoxy Resins, by Henry Lee and KrisNeville, McGraw-Hill, Inc., 1967, which is hereby incorporated byreference. One preferred epoxy resin polymer for use in the presentinvention is diglycidyl ether of bisphenol A (DGEBA) which has thefollowing structural formula: ##STR2## wherein n is an integer from 0 to18, desirably from 0 to 14.3, and preferably from 0 to 5.5. The averagemolecular weight of DGEBA is from about 340 to about 4000, andpreferably from about 340 to 2600. Another preferred epoxy resin polymerfor use in the present invention is polyglycidyl ether ofphenol-formaldehydenovolac[polyphenolformaldehydepoly(2,3-epoxypropyl)ether] or epoxynovolac resin which has the following structural formula: ##STR3##wherein n has a value of about 1.6.

The unsaturated monocarboxylic acids useful in the formation of theprereacted vinyl ester base resin used in the present invention includealiphatic and aromatic types. If the unsaturated mono carboxylic acid isaliphatic, it desirably contains 2 to 6 carbon atoms with preferredexamples thereof being acrylic acid, methacrylic acid, itaconic acid,halogenated acrylic or methacrylic acids, or hydroxyalkyl acrylate ormethacrylate half esters of dicarboxylic acids, wherein the hydroxyalkylgroup preferably contains 2 to 6 carbon atoms, as described in U.S. Pat.No. 3,367,992 which is hereby fully incorporated by reference. If anaromatic unsaturated monocarboxylic acid is utilized, cinnamic acid ispreferred. Blends of acrylic, methacrylic, itaconic, halogenated acrylicor methacrylic, and/or cinnamic acids may also be utilized. The use ofmethacrylic acid is highly preferred.

Suitable types of statistical dicarboxyl-terminated liquid rubbers whichhave been found satisfactory for use in the formation of the base resinof the invention, are manufactured by the assignee of the presentinvention, B. F. Goodrich Chemical Co., and are sold under thetrademarks Hycar CTB, Hycar CTBN, Hycar CTBNX, and the like. Hycar CTBis a carboxyl-terminated butadiene type polymer and may be approximatelyrepresented by the formula:

    HOOC--CH.sub.2 --CH═CH--CH.sub.2 ].sub.x COOH

wherein x represents the number of butadiene units per molecule, with xdesirably being from about 40 to about 300, and preferably from about 75to about 85. Hycar CTB has a functionality of about 2.

Hycar CTBN is a carboxyl-terminated butadiene-acrylonitrile type randomcopolymer which may be approximately represented by the formula:##STR4## wherein x' represents the number of butadiene units permolecule and y represents the number of acrylonitrile units permolecule, with the weight ratio of x' to y being from about 0.9 to about0.1 for the random copolymer containing 10 percent acrylonitrile, fromabout 0.8 to about 0.2 for the copolymer containing 17 percentacrylonitrile, and from about 0.7 to about 0.3 for the copolymercontaining 26 percent acrylonitrile, and with n desirably being fromabout 40 to about 300, and preferably from about 75 to about 85. Thecopolymer has a functionality of from about 1.8 to about 1.85.

Hycar CTBNX is a carboxyl-terminated butadiene-acrylonitrile-acrylicacid terpolymer which may be approximately represented by the formula:##STR5## wherein x" represents the number of butadiene units permolecule, y' represents the number acrylonitrile units per molecule, andz represents the number of acrylic acid units per molecule, and furtherwherein the terpolymer contains from about 17 percent to about 20percent acrylonitrile and preferably has a molecular weight of fromabout 2,000 to about 15,000. The terpolymer has a functionality of about2.3. These and other elastomers having a functional carboxyl terminationat each end of the polymer chain are described more fully in U.S. Pat.No. 3,285,949, which is hereby fully incorporated by reference.

An excess of the selected epoxy resin is reacted with a selecteddifunctional carboxyl-terminated RLP, and an unsaturated monocarboxylicacid. Generally, from about 1 percent to about 30 percent by weight ofRLP and from about 99 percent to about 70 percent of the epoxy isutilized based on the weight of the RLP and the epoxy. An equivalentamount of the unsaturated monocarboxylic acid sufficient to react theexcess amount of epoxy is utilized in the reaction. The reaction may becatalyzed in the conventional manner by tertiary amines such aspyridine, basic compounds such as sodium hydroxide, metal chelates,onium catalysts, triphenyl stibine, triphenyl phosphine and othercatalysts known to those skilled in the art; wherein the preferredcatalyst is pyridine. The reaction may also employ an effective amountof an inhibitor to prevent premature reaction at the acrylic acid doublebonds. Approximately 100 to 600 parts per million of hydroquinonefunctions satisfactorily as a polymerization inhibitor. In forming suchresins, the three ingredients (epoxy resin, unsaturated monocarboxylicacid and carboxyl-terminated elastomer) are mixed. An inhibitor and asuitable catalyst, such as a tertiary amine, is added and the mixture isheated to a suitable reaction temperature generally between roomtemperature and about 175° C. Heating of the reaction mixture continuesuntil the acid value diminishes to a low level, indicating substantiallycomplete reaction between the three reactants, i.e., that the product isfree of unreacted epoxide groups and carboxylic acid groups. The productresin is directly recovered as a polymerizable thermosetting resinoussubstance.

The neat resin may then be mixed and copolymerized with a suitableethylenically unsaturated monomer such as styrene, alpha methyl styrene,or an unsaturated aromatic compound such as vinyl toluene, with styrenebeing preferred. Other suitable ethylenically unsaturated monomers arethose listed in U.S. Pat. Nos. 3,367,992 and 3,683,045, which are herebyfully incorporated by reference.

The following reactions occur during formation of the prereacted vinylester base resin useful in the present invention:

1. Epoxy Resin plus Hycar CTB, CTBN or CTBNX ##STR6##

2. Epoxy Resin plus Methacrylic Acid ##STR7##

3. Elastomer-Epoxy Intermediate plus Methacrylic Acid ##STR8## dependingon whether Hycar CTB, Hycar CTBN, or Hycar CTBNX, which are fullydescribed hereinabove, is utilized as the RLP.

The prereacted vinyl ester resin utilized as a starting material in thepresent invention is a mixture of the reaction products of reactions 2and 3 outlined above.

The styrene-containing prereacted vinyl ester base resin may then beformed into a hard usable product by reacting the double bonds in thepresence of a peroxide such as benzoyl peroxide. With regard to thepreparation of the prereacted vinyl ester resin starting materialutilized in the formation of the modified vinyl ester resin compositionof the present invention, U.S. Pat. Nos. 3,892,819 and 3,928,491 arehereby fully incorporated by reference.

In accordance with one of the main features of the present invention,selected RLP additives are admixed with the prereacted vinyl ester baseresin material set forth above. Various RLP types may be utilized foradmixing into the prereacted vinyl ester resin, including nonfunctional,monofunctional and/or difunctional forms of a selected type. Examples ofsuitable RLP additives include carboxyl-terminated butadiene typepolymers and carboxyl-terminated butadiene-acrylonitrile typecopolymers. The formation of the statistical difunctional form of suchcarboxyl-terminated polymers is fully described in U.S. Pat. No.3,285,949 which is hereby fully incorporated by reference. Thenonfunctional butadiene-acrylonitrile copolymer is well known to the artand to the literature.

With regard to the statistical monofunctional form of suchcarboxyl-terminated polymers, it is made by reacting a vinyl-containingmonomer with a difunctional initiator as well as a nonfunctionalinitiator and can be generally indicated by the structural formula:##STR9## wherein ##STR10## is derived from the difunctional initiatorand --Y is derived from the nonfunctional initiator and wherein --PB--represents the carbon-carbon backbone of the polymer. Generally, thedifunctional carboxyl-terminated polymer is generally represented by thestructural formula ##STR11## The statistical monofunctionalcarboxyl-terminated polymers will contain generally a small or minorityamount of polymers generally represented by the structural formula

    Y--PB--Y

wherein Y is derived from a nonfunctional initiator. Regardless of theamounts of the various difunctional, or monofunctionalcarboxyl-terminated polymers, as well as the nonfunctional terminatedpolymers, the overall statistical monofunctional carboxyl-terminatedpolymeric compositions generally contain from about 0.25 to about 4.5percent by weight of carboxyl groups based upon the total weight of thestatistical polymeric composition and have an acid number of from about3.0 to about 52.

The non-reactive terminus --Y of the molecule is referred to as suchbecause it will not undergo condensation, as compared to the carboxylterminus which will undergo that type of reaction. The composition ofthe terminus will vary depending upon the polymerization initiatorsused, however suitable groups include an alkyl or a nitrile.

The backbone --PB-- of the statistical carboxyl-terminated polymercomprises repeating units made from any monomer which is polymerizableby any free radical reaction mechanism. The repeating unit compositionof the polymer backbone may be made from a single monomer (homopolymer)or two or more monomers (copolymer). Preferably, the polymeric backbonesare derived from at least one vinyl monomer having at least one terminalvinyl (CH₂ ═) group and up to 18 carbon atoms. Examples of suitablevinyl monomers include olefins having from 2 to 10 carbon atoms such asethylene, isobutylene, dienes containing 4 to 10 carbon atoms,preferably 4 to 8 carbon atoms, such as butadiene, isoprene(2-methyl-1,3-butadiene), 2-isopropyl-1,3-butadiene and chloroprene(2-chloro-1,3-butadiene); vinyl and allyl esters of carboxylic acidscontaining 2 to 8 carbon atoms such as vinyl acetate, vinyl propionateand allyl acetate; vinyl and allyl ethers of alkyl radicals containing 1to 8 carbon atoms such as vinyl methyl ether and allyl methyl ether; andacrylates having the formula ##STR12## wherein R is hydrogen or an alkylradical containing 1 to 3 carbon atoms, such as methyl, ethyl, propyl,and isopropyl; R¹ is an alkyl radical containing 1 to 18 carbon atoms,preferably 1 to 8 carbon atoms, or an alkoxyalkyl, alkylthioalkyl, orcyanoalkyl radical containing 2 to 12 carbon atoms, preferably 2 to 8carbon atoms. Preferably, R¹ is an alkyl radical containing 1 to 8carbon atoms. Suitable acrylates include ethyl acrylate, butyl acrylate,hexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecylacrylate, methoxyethyl acrylate, butoxyethyl acrylate, hexylthioethylacrylate, α-cyanoethyl acrylate, cyanooctyl acrylate, methylmethacrylate, ethyl methacrylate, octyl methacrylate and the like. Thepolymeric backbone may comprise homopolymers of the above vinyl monomersor copolymers of two or more of the monomers.

The vinyl monomers described above may also be polymerized readily withup to about 50 percent by weight, but preferably up to about 35 percentby weight, of at least one comonomer such as a vinyl aromatic having theformula ##STR13## wherein R² is hydrogen or methyl and R³ is an aromaticmoiety having from 6 to 15 carbon atoms resulting in compounds such asstyrene, α-methyl styrene, chlorostyrene, and vinyl toluene; a vinylnitrile having the formula ##STR14## wherein R⁴ is hydrogen or methyl,resulting in compounds such as acrylonitrile and methacrylonitrile,respectively; vinyl acids having from 3 to 12 carbon atoms such asacrylic acid, methacrylic acid, and itaconic acid; an amide ofolefinically unsaturated carboxylic acids containing 2 to 8 carbon atomssuch as acrylamide and methacrylamide; or an allyl alcohol having from 3to 10 carbon atoms.

Examples of suitable polymeric backbones include homopolymers ofpolyisoprene, polybutadiene, poly(vinylethylether), poly(ethylacrylate)and poly(butylacrylate); copolymers of butadiene and acrylonitrile,butadiene and styrene, vinyl acetate and isoprene, vinyl acetate andchloroprene, methyl acrylate and butadiene, methyl acrylate and ethylacrylate, methyl acrylate and butyl acrylate, methyl acrylate and2-ethylhexyl acrylate, ethyl acrylate and ethylene, ethyl acrylate andisobutylene, ethyl acrylate and isoprene, ethyl acrylate and butadiene,ethyl acrylate and vinyl acetate, ethyl acrylate and styrene, ethylacrylate and chlorostyrene, ethyl acrylate and n-butyl acrylate, ethylacrylate and 2-ethylhexyl acrylate; ethyl acrylate and acrylic acid;ethyl acrylate and acrylamide; butyl acrylate and styrene; butylacrylate and acrylonitrile; butyl acrylate and vinyl chloride;terpolymers of butadiene, acrylonitrile, and acrylic acid; ethylacrylate, styrene and butadiene; and ethyl acrylate, n-butyl acrylateand 2-ethylhexyl acrylate.

One group of preferred low viscosity monofunctional carboxyl-terminatedpolymers have copolymeric backbones comprising from about 50 percent toabout 99 or 100 percent by weight of a diene monomer, such as isopreneor butadiene, and up to about 50 percent by weight of a vinyl nitrilecomonomer, such as acrylonitrile, or a vinyl aromatic such as styrene.The acrylonitrile content preferably is from about 10 percent to about35 percent, desirably, is from about 16 percent to about 26 percent, andmost preferably about 16 percent. Such polymers have a carboxyl contentof from about 0.4 percent to about 10 percent by weight, preferably 0.4percent to about 2.5 percent by weight, based upon the total weight ofthe polymer. These polymers have a number average molecular weight offrom about 1000 to about 12,000.

The greatest advantage provided by these polymers is that theirviscosity is approximately one-half (1/2) the value of an equivalentcommercially known difunctional carboxyl-terminated polymer. This isdemonstrated by the measured viscosities summarized in the followingTable I, which compares the viscosity of the precursor statisticalmonofunctional polymers versus difunctional carboxyl-terminated polymershaving the same compositions of butadiene homopolymers orbutadiene/acrylonitrile copolymers.

Polymers "A" and "a" are homopolymers of butadiene while polymers B/b -D/d are butadiene/acrylonitrile copolymers. The polymer designations inupper case letters represent the precursor statistical monofunctionalcarboxyl-terminated polymers while the lower case letters representstructurally equivalent difunctional carboxyl-terminated polymers. Thedesignation "EPHR" stands for Equivalents of Carboxyl Per Hundred Partsof Rubber.

                  TABLE I                                                         ______________________________________                                        Comparative Viscosity of Statistical Monofunctional                           vs. Difunctional Carboxyl Terminated Polymers                                         Acrylonitrile                                                                 Content     Viscosity       Carboxyl                                  Polymer (% by weight)                                                                             (mPa'S @ 27° C.)                                                                       EPHR                                      ______________________________________                                        A       --          22,600          0.022                                     a       --          60,000          0.045                                     B       10.2        30,600          0.025                                     b       10.2        60,000          0.050                                     C       16.8        65,000          0.022                                     c       16.8        135,000         0.052                                     D       25.9        202,000         0.024                                     d       25.9        500,000         0.057                                     ______________________________________                                    

It will be appreciated by one skilled in the art that the viscosity ofindividual polymers will vary depending upon the monomeric compositionof the polymeric backbone. However, generally the viscosity ranges fromabout 10,000 mPa's to about 1.5 million mPa's. For polymers ofpolybutadiene or polybutadiene and acrylonitrile wherein theacrylonitrile content ranges from 0 percent to about 50 percent byweight of the polymer, the viscosity ranges from about 12,000 mPa's toabout 1.5 million mPa's, preferably 15,000 mPa's to about 1 millionmPa's.

Thus, the above-described low viscosity statistical monofunctionalcarboxyl-terminated polymers which are generally liquids, are useful asa toughening and/or flexibilizing agent for any thermoset resin system.Thermoset resins include, but are not limited to, vinyl esters,epoxides, phenolics, alkyds and polyesters. Specific system applicationscan be at ambient temperatures and include those rich in resin and thoserich in rubber. Resin rich system applications include one and two partadhesives, especially adhesives made of thermoset resins such as vinylesters and epoxy, for uses including structural adhesives in the marine,automotive and aircraft industries; electrical and electronic pottingcompounds and encapsulants; cast pipe; sheet molding compound other thanepoxy; and bulk molding compound. Castable rubber rich systemapplications include rocket and missile fuel binders; and constructionand civil engineering applications including roofing, flooring,water-impermeable membranes, and crack sealers.

As discussed earlier hereinabove, the significantly lowered viscosityattaches substantial advantages over known difunctional polymers.Typically, the viscous difunctional polymers require warming to reducetheir viscosity and render them more workable, especially in the field.The present precursor low viscosity statistical monofunctional polymersdo not require warming prior to use and will be preferred forapplications which must be performed at relatively lower ambienttemperatures. Additionally these polymers provide faster air release andbetter mixing. Therefore, these polymers will be preferred forapplications involving mixing, which tends to entrap air, which mustthen be released before continuing, such as with on-site structuralrepair jobs.

These polymers have further utility in that they also may be reacted toproduce polymers having terminal functional groups other than carboxyls,such as amines or epoxies.

The statistical monofunctional carboxyl-terminated polymer can be madeby any conventional addition polymerization technique employing a freeradical mechanism. Generally, the reaction is conducted by mixing one ormore backbone-forming monomers with a mixture of a difunctional andnonfunctional initiator, and a solvent, then heating. The monomers canbe one or more of the polymerizable monomers described hereinabove.

The initiator is a mixture or blend of two different initiators, namelya difunctional initiator and a nonfunctional initiator, capable ofinitiating a free radical polymerization.

Considering the difunctional initiator, any difunctional initiator canbe used. However, one skilled in the art will appreciate that when adifunctional initiator other than an organic acid is used, conversion ofthe terminal groups to acid groups will be required. For example, thehydroxyl groups on hydrogen peroxide or hydroxy ethyl disulfide requireconversion to acid groups. Conventional methods may be used toaccomplish the conversion such as by reaction with a cyclic acidanhydride, for example succinic anhydride. Preferably the difunctionalinitiator is an organic azo compound or a peroxide. The organic azoinitiator preferably is a bis-azocyano acid having the formula ##STR15##wherein R⁵ is an alkyl group of 1-3 carbon atoms, and n is an integerfrom 0 to 6. The preferred acids include azodicyanobutyric acid andazodicyanovaleric acid (ADVA), with ADVA being the most preferred. Thepreparation of these materials is known and disclosed in U.S. Pat. Nos.3,285,949 and 2,520,338, which are incorporated herein by reference. Theorganic azo initiator decomposes to form N₂ gas and free radicals havingthe formula ##STR16## with the portion thereof having the structuralformula ##STR17## being represented by --X-- in the structural formulashown above for the monofunctional carboxyl-terminated polymer. Theaction of this type of initiator is due to the fact that the azocarbon-nitrogen bond is readily dissociated, as by thermal means.

The preferred difunctional peroxide initiator has the formula ##STR18##wherein R⁶ is an alkyl group having from about 2 to about 6 carbonatoms, and preferably 3 carbon atoms. A desirable peroxide is succinicacid peroxide and a preferred peroxide is glutaric acid peroxide. Thedifunctional peroxide initiator decomposes to form CO₂ gas and freeradicals having the formula

    HOOC--R.sup.6.

wherein R⁶ is represented by X in the structural formula shown above forthe monofunctional carboxyl-terminated precursor polymer. The action ofthis type of initiator is due to the fact that the peroxideoxygen-oxygen bond is readily dissociated, as by thermal means.

Considering the nonfunctional initiator, any nonfunctional azo orperoxide initiator can be used. Preferably the azo initiator is abis-azocyano having the formula ##STR19## wherein R⁷ is an alkyl groupof 1-3 carbon atoms and n is an integer from 0 to 6. Such compounds areknown and disclosed in U.S. Pat. No. 2,556,876. The preferred compoundis 2,2'-azobis(2-methylpropionitrile) also known as AIBN. The azoinitiator decomposes to form N₂ gas and free radicals having the formula##STR20## which is represented by --Y as the non-reactive terminus ofthe precursor monofunctional carboxyl-terminated polymer describedabove. The action of this type of initiator also is due to the fact thatthe azo carbon-nitrogen bond is readily dissociated, as by thermalmeans.

The nonfunctional peroxide initiator preferably is an acyl peroxidehaving the formula ##STR21## wherein R⁸ is an aromatic, or anunsubstituted or a substituted alkyl group desirably having from about 1to about 15 and preferably from about 1 to about 6 carbon atoms.Desirable peroxides include diacetyl peroxide, dilauryl peroxide,didecanoyl peroxide, and diisononanoyl peroxide, with dibenzoyl peroxidebeing preferred. The nonfunctional peroxide initiator decomposes to formCO₂ gas and free radicals having the formula R⁸ which also isrepresented by Y as the non-reactive terminus of the precursormonofunctional carboxyl-terminated polymer described above. The actionof this type of initiator is also due to the fact that the peroxideoxygen-oxygen bond is readily dissociated, as by thermal means.

The amount of initiators present, on a mole basis, may vary from about0.2 percent to about 90 percent difunctional initiator and from about 10percent to about 99.8 percent nonfunctional initiator. Preferably fromabout 30 percent to about 75 percent difunctional initiator is used incombination with from about 70 percent to about 25 percent nonfunctionalinitiator. Most preferred is from about 60 percent to about 40 percentdifunctional initiator in combination with from about 40 percent toabout 60 percent nonfunctional initiator. As noted, one skilled in theart will appreciate that the monofunctional polymer product is a blendor mixture of molecules having different end groups, namely amonofunctional species, a difunctional species and a nonfunctionalspecies. When the ideal 50/50 blend of difunctional and nonfunctionalinitiators is used, it is expected that statistically one obtains, byweight, from about 5 percent to about 90 percent difunctional specie,from about 90 percent to about 5 percent nonfunctional specie, and about5 percent to about 5 percent monofunctional specie; desirably from about10 percent to about 50 percent difunctional specie, from about 10percent to about 50 percent nonfunctional specie, and up to about 50percent monofunctional specie; and preferably about 25 percentdifunctional specie, about 25 percent nonfunctional specie and about 50percent monofunctional specie. When other ratios of difunctional andnonfunctional initiators are utilized, it will be appreciated that theend amount of the nonfunctional terminated polymer as well as thedifunctional terminated polymer will generally vary in accordance withthe ratio of the difunctional polymer to the nonfunctional polymer, butthat the amount of the monofunctional specie will generally be no higherthan 50 percent. However, as noted above, the blend or mixture of thestatistical monofunctional carboxyl-terminated polymer desirably has anaverage functionality per polymer of approximately 1.

The liquid polymerization products can be prepared in any solvent forthe initiators, the monomers or the polymers. The solvent is desirablylow boiling so it can be readily removed. Such solvents are generallypolar and do not act as chain transfer agents. Examples of such solventsinclude the various ketones having from 2 to about 10 carbon atoms,various alcohols having from 1 to about 7 carbon atoms, various aromaticcompounds having from about 6 to about 10 carbon atoms, various estersof a carboxylic acid wherein the ester portion has up to about 4 carbonatoms and the dicarboxylic acid has from about 2 to about 3 or 4 carbonatoms in the non-ester portion, and various ethers including internalethers having from about 3 to about 7 carbon atoms. Specific examples ofsuitable solvents include acetone, methyl ethyl ketone, 2-pentanone,3-pentanone, methyl isobutyl ketone, methyl alcohol, ethyl alcohol,n-propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol,sec-butyl alcohol, tert-butyl alcohol, benzene, toluene, methyl acetate,ethyl acetate, propyl acetate, and tetrahydrofuran. Acetone ispreferred. The reaction temperature may range from about 40° C. to about120° C., desirably 60° C. to about 100° C., and preferably from about70° C. to about 90° C. The number average molecular weight (Mn) of theprecursor statistical monofunctional carboxyl-terminated polymers rangesfrom about 1,000 to about 12,000, based upon size exclusionchromatography method of determination.

Those skilled in the art will appreciate that in order to form a polymerhaving uniform composition throughout the charge and maintain constantmolecular weight over the length of the polymerization, the initiator,and comonomer if copolymerizing, must be continuously metered throughoutthe polymerization. Therefore, the statistical monofunctionalcarboxyl-terminated polymers are made by a method whereby initially, thereactor is charged with monomer, and a small amount of initiator mixtureand comonomer if copolymerizing, and all of the polymerization solvent.The exact amounts of monomers and initiator will vary depending upon theproduct polymer, however, the amounts can be readily determinedexperimentally by conventional methods of calculation. Then, afterbringing the reaction mixture to reaction temperature, more initiator,and comonomer if copolymerizing, are added during polymerization suchthat they are continuously metered including incremental addition or aplurality of batch additions, etc. throughout polymerization.Conventional procedures including incremental addition or a plurality ofbatch additions can be used to recover the resulting reaction products.

No emulsifier is necessary for this process. After polymerization it maybe desirable to add conventional additives to the polymer, dependingupon its end use, such as thermal stabilizers, including Geltrol®commercially available from The B. F. Goodrich Company, Akron, Ohio,U.S.A.

The above-described process for forming the statistical monofunctionalcarboxyl-terminated polymer will be better understood by the followingexamples.

EXAMPLE 1

The statistical monofunctional carboxyl-terminated polymer was obtainedin the following experiment. A 20 gallon reactor was cooled to 25° C.and evacuated to suck in 2.08 Kg acrylonitrile, 6.12 Kg acetone and 0.99Kg initiator solution, in sequence. The initiator solution concentrationWas 10.3 percent ADVA and 6.03 percent AIBN. The reactor was evacuateduntil the acetone boiled (about 20-25" Hg), then pressured to 20 psiwith nitrogen. This was repeated and the reactor once again evacuated to20" Hg. The vacuum was broken by charging 38.0 lbs. of butadiene. Themixture was heated to reaction temperature of 85° C. and allowed toreact for approximately 13 hours. During polymerization, additionalinitiator mixture and acrylonitrile were metered into the reactionvessel. Conventional techniques were used to recover the product whichhad an acid number of 12.9, viscosity at 27° C. of 65,000 mPa's and abound acrylonitrile content of 16.5 percent.

EXAMPLE 2

The statistical monofunctional carboxyl-terminated polymer was obtainedin the following experiment. A 15 gallon reactor was cooled to 25° C.and evacuated to suck in 3.52 Kg acrylonitrile, 5.58 Kg acetone and 2.72Kg initiator solution, in sequence. The initiator solution concentrationwas 8.0 percent ADVA and 4.7 percent AIBN. The reactor was evacuateduntil the acetone boiled (about 20-25" Hg), then pressured to 20 psiwith nitrogen. This was repeated and the reactor once again evacuated to20" Hg. The vacuum was broken by charging 30.22 lbs. of butadiene. Themixture was heated to reaction temperature, 75° C. and allowed to reactfor approximately 26 hours. During polymerization, additional initiatormixture and acrylonitrile were metered into the reaction vessel.Conventional techniques were used to recover the product which had anacid number of 13.3, viscosity at 27° C. of 202,000 mPa's and a boundacrylonitrile content of 25.9 percent.

Physical property evaluations conducted on polymer samples to comparethe performance of the statistical monocarboxyl-terminated polymers toconventional dicarboxyl-terminated polymers in a model two-part epoxysystem generally showed that for epoxy recipes containing up to 10 partspolymer, the statistical monocarboxyl-terminated polymers exhibitedcomparable or superior fracture energies (G_(Ic)) to those observed inthe conventional dicarboxyl-terminated polymers.

Another suitable RLP additive for use in the present invention isdifunctional carboxyl-terminated butadiene-acrylonitrile-acrylic acidtype terpolymer which was described hereinabove for the formation of theprereacted vinyl ester base resin, with the foregoing description herebybeing fully incorporated by reference.

Still other suitable elastomers which can be utilized as RLP additivesin the present invention are epoxy-terminated type polymers, with thestatistical difunctional form thereof being fully described in U.S. Pat.No. 4,530,962 which is hereby fully incorporated by reference. Thenonfunctional butadiene-acrylonitirle copolymer is well known to the artand to the literature.

With regard to the statistical monofunctional form of theepoxy-terminated reactive liquid polymer, the precursor statisticalmonofunctional carboxyl-terminated polymer is once again utilized. Thepreparation, structure, formulation, and the like of the statisticalcarboxyl-terminated prepolymer is set forth hereinabove and accordinglyis fully incorporated by reference with regard to the structure,formulation, and preparation thereof. Inasmuch as the statisticalepoxy-terminated polymer composition is prepared by reacting one or moreepoxy resins as set forth hereinbelow with a statistical monofunctionalcarboxyl-terminated polymer composition, the actual composition willcontain various monofunctional epoxy-terminated polymers which can berepresented by the general structural formula ##STR22## variousdifunctional polymers which can be represented by the general structuralformula ##STR23## and various nonfunctional polymers which can berepresented by the general structural formula Y--PB--Y, wherein X, PB,and Y are as set forth hereinabove, and wherein EPOXY is an epoxy resinwhich is reacted with the statistical monofunctional carboxyl-terminatedpolymer composition. Naturally, it is to be understood that duringreaction with the statistical monofunctional carboxyl-terminatedcomposition, ring opening reaction takes place. The reaction between theepoxy resin and the statistical monofunctional carboxyl-terminatedpolymer composition which will be described in more detail hereinbelowgenerally takes place in the presence of an inert atmosphere at elevatedtemperatures utilizing small amounts of catalysts.

Considering the "EPOXY" group, it is generally an epoxy resin usuallyknown to the art and to the literature and can be various commerciallyavailable epoxy resins. Examples of specific epoxy resins or polymerswhich can be utilized include: polyhydric phenol polyether alcohols;glycidyl ethers of novolac resins such as epoxylated phenol-formaldehydenovolac resin; glycidyl ethers of mono-, di-, and trihydric phenols;glycidyl ethers of bisphenols such as diglycidyl ether oftetrabromobisphenol A; glycidyl ethers of polynuclear phenols; epoxyresin made from diphenolic acid; glycidyl ethers of aliphatic polyolssuch as chlorine-containing aliphatic diepoxy and polyepichlorohydrin;glycidyl esters such as aliphatic diacid glycidyl esters and epoxidizedphenolphthalein; glycidyl epoxies containing nitrogen such as glycidylamides and amide-containing epoxies; glycidyl derivatives of cyanuricacid; glycidyl resins from melamines; glycidyl amines such astriglycidyl ether amine of p-aminophenol andbis(2,3-epoxy-propyl)methylpropylammonium p-toluenesulfonate; glycidyltriazines; thioglycidyl resins such as epoxidized bisulfide;silicon-glycidyl resins such as1,4-bis[(2,3-epoxypropoxy)dimethylsilyl]; and fluorine glycidyl resins.Other epoxy resins which can be used include those which are synthesizedfrom mono-epoxies other than epihalohydrins including epoxy resins madefrom unsaturated monoepoxies such as polyallyl glycidyl ether andglycidyl sorbate dimer; epoxy resins from monoepoxy alcohols; epoxyresins from monoepoxies by ester interchange; epoxy resins fromglycidaldehyde; polyglycidyl compounds containing unsaturation such asallyl-substituted diglycidyl ether of bisphenol A; epoxy resins whichare synthesized from olefins and chloroacetyls such as butadienedioxide, vinylcyclohexene dioxide, epoxidized polybutadiene, andbis(2,3-epoxycyclopentyl)ether, and epoxy-resin adducts of the above. Amore comprehensive list of epoxy resins can be found in Handbook ofEpoxy Resins, by Henry Lee and Kris Neville, McGraw-Hill, Inc., 1967,which is hereby incorporated by reference. A highly preferred epoxyresin for use is diglycidyl ether of bisphenol A (DGEBA) which has thefollowing formula: ##STR24## wherein n is an integer from 0 to 18,desirably from 0 to 14.3, and preferably from 0 to 5.5.

The various epoxy resins or polymers generally have a number averagemolecular weight of from about 200 to about 13,000. The various epoxypolymers generally are difunctional, that is, they have two epoxidegroups typically at the terminal portions thereof. The amount of theepoxy resin utilized is such that the mole ratio of epoxy resin to thestatistical carboxyl-terminated monofunctional polymer is generally inexcess, as from about 0.90 to about 40, desirably from about 0.90 toabout 20, and preferably from about 0.95 to about 1.05. Thus, free epoxyresins will generally exist within the reacted statisticalmonofunctional epoxy-terminated reactive liquid rubber polymericcompositions.

Reaction of the various epoxy resins or polymers with the statisticalcarboxyl-terminated reactive polymers generally occurs at elevatedtemperatures in the presence of an inert atmosphere. Generally, anyinert gas can be utilized such as nitrogen, argon, and the like. Thereaction generally occurs at temperatures of from about 80° C. to about180° C, desirably from about 90° C. to about 140° C., and preferablyfrom about 90° C. to about 120° C., generally in the presence of ambientor normal atmospheric temperature. In order to promote reaction,conventional epoxy catalysts are optionally utilized.

One group of catalysts which can be utilized are the various organicphosphines having from 3 to 40 carbon atoms which include various alkyl,various aromatic, various alkyl substituted aromatic, etc., phosphinessuch as triphenyl phosphine, diethylphenylphosphine,dimethylphenylphosphine, tribenzyl phosphine, tri-n-butylphosphine,tri-t-butylphosphine, tricyclohexylphosphine, triethylphosphine,trimethylphosphine, tri-n-octylphosphine, triphenylphosphine,tris(3-chlorophenyl)phosphine, tris(4-chlorophenyl)phosphine,tris(4-fluorophenyl)phosphine, tris(2-hydroxyphenyl)phosphine,tris(3-methoxyphenyl)phosphine, tris(4-methoxyphenyl)phosphine,tris(2-tolyl)phosphine, and tris(3-tolyl)phosphine. A second type ofcatalyst are the various tertiary amines wherein the hydrocarbyl portionis generally an aliphatic and preferably an alkyl group, an aromaticgroup, or an aliphatic substituted aromatic, or an aromatic substitutedaliphatic group, having a total of from about 1 to about 10 carbon atomswith from about 1 to about 6 carbon atoms being preferred. Examples ofspecific tertiary amine catalysts include benzyl dimethyl amine,trimethyl amine, triethylamine, and the like. Another group of suitablecatalysts are the various alkyltriphenylphosphonium ester or halidesalts wherein the alkyl group generally has from 1 to about 10 carbonatoms, and wherein iodide is the preferred halide salt. Examples of suchspecific catalysts include ethyltriphenylphosphonium acetate,ethyltriphenylphosphonium iodide, n-hexyltriphenylphosphonium bromide,isobutyltriphenylphosphonium bromide, isopropyltriphenylphosphoniumbromide.

As noted, although generally desired, the catalysts are optional andhence may not be utilized. When utilized, the amount thereof isgenerally up to about 1 percent by weight based upon a total weight ofthe epoxy resin and the statistical monofunctional carboxyl-terminatedreactive polymer, desirably up to about 0.5 percent by weight, andpreferably from about 0.001 to about 0.1 percent by weight.

In order to reduce the level of residual reactions, the formedmonofunctional epoxy-terminated reactive polymers desirably have a lowacid number, such as 2.0 or less, and preferably 0.4 or less. Moreover,the epoxy-terminated reactive polymers also have very low viscosities,such as generally less than 2,000,000 mPa's, desirably 1,000,000 mPa'sor less, and preferably 500,000 mPa's or less.

Inasmuch as the epoxy resins react with available carboxyl-terminatedfunctional end groups, the overall make-up or content of the statisticalepoxy-terminated reactive liquid rubber polymers will generally containthe same ratios or amounts of reactive epoxy-terminated end groups asthe statistical carboxyl-terminated polymers. Thus, if the statisticalcarboxyl-terminated polymers are made utilizing approximately 50 percentof a difunctional initiator and 50 percent of a nonfunctional initiator,the statistical epoxy-terminated polymers will contain generally fromabout 5 percent to about 90 percent of the difunctional specie, fromabout 90 to about 5 percent of the difunctional specie, and from about 5percent to about 50 percent of the monofunctional specie; desirably fromabout 10 to about 50 percent of the difunctional specie, from about 10to about 50 percent of the nonfunctional specie, and up to about 50percent of the monofunctional specie; and preferably about 25 percent ofthe difunctional specie, about 25 percent of the nonfunctional specie,and about 50 percent of the monofunctional specie. Hence, as notedabove, it is termed a statistical epoxy-terminated monofunctionalreactive liquid rubber polymer composition. The ratios of the variousspecies of the statistical polymer will vary depending upon the amountof initiators generally utilized and hence the amount of thedifunctional or nonfunctional species can vary widely with the amount ofthe monofunctional specie can generally not be greater than 50 percent.

The statistical epoxy-terminated monofunctional polymers are generallyliquid but can also be solid and have significantly lower viscositiesthan heretofore conventional but difunctional epoxy-terminated polymers,which render them more workable, especially in the field. Suitableapplications include ambient temperature use as well as use inassociation with vinyl ester resins and epoxy resins as structuraladhesives in the marine, automotive, and aircraft industries; electricaland electronic prodding compounds and encapsulants; cast pipe; sheetmolding compounds, boat molding compounds, and the like. They can alsobe utilized as castable systems in construction and civil engineeringapplications such as roofing, flooring, water-impermeable membranes,cracks sealers, and the like.

The formation of the statistical monofunctional epoxy-terminated polymerwill be better understood by reference to the following examples.

EXAMPLE 3

To a suitably sized reaction vessel was charged 400 grams of polymer Cand 34.7 grams of Epon 828, that is, DGEBA, at a molar ratio ofapproximately 1:1. 0.05 grams of triphenyl phosphine was added as acatalyst. In the presence of a nitrogen blanket, the temperature of thereaction vessel was raised to approximately 130° C. and the reactioncontinued until the acid number was generally less than 0.6. Thereaction time was approximately 20 hours to reach completion. Thestatistical epoxy-terminated reactive polymer had a viscosity of 339,000mPa's at 27° C. In contrast, a similar reaction utilizing a difunctionalcarboxyl-terminated reactive polymer yielded a viscosity in excess of2,000,000.

EXAMPLE 4

An epoxy-terminated reactive polymer was made utilizing the sameprocedure as in Example 3 except that Polymer D and 600 grams of Epon828 was utilized. The molar ratio was thus approximately 17.3. Nocatalyst was utilized and the reaction was completed in about 4.5 hours.The statistical epoxy-terminated reactive polymer had a viscosity of91,000 mPa's at 27° C. In contrast, a control utilizing the samereactants and amounts except that a difunctional carboxyl-terminatedreactive polymer was utilized, yielded a product having a viscosity offrom about 300,000 to about 600,000 mPa's at 25° C.

EXAMPLE 5

In a suitably sized reaction vessel was added equal parts by weight ofpolymer D and the diglycidyl ether of cyclohexane dimethanol. Under ablanket of nitrogen, the reaction temperature was raised to 130° C. andreacted until the Acid No. was <0.6. The reaction required 4.5 hours toreach completion. The final product had a viscosity of 8600 mPa's at 27°C. (The same reaction with a standard difunctional RLP gives an adductwith a viscosity of 15,000-25,000 mPa's at 25° C.) Molar RatioRLP/Epoxy--1:8.6

EXAMPLE 6

In a suitably sized reaction vessel was added 200 parts by weight ofpolymer D and 300 parts of an epoxy novolac (such as DEN-438). Under ablanket of nitrogen was added 2.5 grams (0.5 weight percent) ofphosphonium iodide and the reaction temperature was raised to 100° C.The reaction required only 1 hour to reach the desired end point of notitratable acid. The final adduct had a viscosity of 160,000 mPa's at50° C. and 1,980,000 mPa's at 27° C. (There is no comparable adduct witha difunctional RLP).

Another RLP found suitable for admixing as an additive into theprereacted vinyl ester resin starting material utilized in the presentinvention, is the statistically difunctional hydroxyl-terminatedepihalohydrin type polymer having a number average molecular weight ofabout 3300, which is described in U.S. Pat. No. 3,850,856 and is herebyfully incorporated by reference.

Still other suitable RLPs found useful for admixing as an additive intothe prereacted vinyl ester base resin are the vinylidene-terminated typepolymers described in U.S. Pat. No. 3,910,992, which is hereby fullyincorporated by reference.

Epoxy-terminated butadiene-acrylonitrile type copolymer additivecontaining 17 percent or 26 percent bound acrylonitrile is preferred foradmixing into the prereacted vinyl ester resin starting material in thepresent invention. It is understood that other RLPs can be utilized foradmixing as an additive into the prereacted vinyl ester base resin,including but not limited to, RLPs having functional groups substitutedalong the backbone of the polymer rather than on the ends thereof asdescribed above.

A selected one of the above-described RLP additives or a blend of thestatistically different forms thereof are admixed with the prereactedvinyl ester base resin to form the modified vinyl ester resincomposition of the present invention in the following manner.

In accordance with another of the main features of the presentinvention, the selected RLP additive is admixed in a conventional mannerwith the prereacted vinyl ester base resin and a suitable curing agentis added to the RLP/base resin admixture. Although addition of the RLPadditive preferably occurs prior to cure of the base resin, it isunderstood that the RLP additive could be admixed into the resin systemduring cure in the presence of heat without affecting the concept of thepresent invention. From about 2 to about 30 parts, desirably from about2 to about 20 parts, and preferably from about 2 to about 10 parts ofthe RLP additive based on 100 parts of the base resin, is admixed withthe base resin. It is well known to the art and to the literature thataddition of amounts of the RLP additive greater than about 30 parts per100 parts of the base vinyl ester resin would result in reduction in thethermomechanical properties of the base resin.

Suitable curing agents include free radical curing agents such as freeradical peroxides which are well known to those skilled in the art. Suchcuring agents are utilized in an amount of from about 0.5 to about 4parts, and preferably from about 1 to about 2 parts per 100 parts of thebase resin. The system then is cured in a conventional Teflon ®-coatedaluminum mold and heated for 1 hour at from about 40 to about 80° C.with 60° C. being preferred, and then for an additional 2 hours at fromabout 100 to about 150° C. with 120° C. being preferred.

In accordance with one of the key features of the present invention,although not being fully understood, it is believed that admixture ofthe RLP additive with the prereacted vinyl ester base resin andsubsequent heating during cure of the resin system causes the RLPadditive to miscibilize or become uniformly dispersed with the baseresin, thus generally preventing phase separation of the RLP additiveand the base resin. More particularly, it is thought that the rubberparticles of the RLP additive physically associate or affiliate with therubber particles previously reacted into the backbone of the base resindue to the similarity and polarity of the elastomers, and further due tothermodynamic factors which occur during mixing of the free RLP into thebase resin and heating of the resin system during cure. Moreover, it isthought that the prereaction of the carboxyl-terminated type RLP withthe epoxy component of the vinyl ester also aids in miscibility betweenthe rubber particles prereacted into the backbone of the vinyl esterresin and the free or unreacted additive rubber particles subsequentlyadmixed into the resin system. Again, it is thought that the rubberparticles of the RLP additive merely physically associate or affiliatewith the rubber particles reacted into the backbone of the base resin,rather than react therewith, so that such additive rubber particles areconsidered to be free or unreacted upon admixture into the base resin.Curing of the admixed resin system in the presence of a suitable curingagent and heat results in the modified vinyl ester resin system of thepresent invention, which is a cross-linked thermoset system.

In accordance with yet another feature of the present invention,admixture of the RLP additive with the prereacted vinyl ester base resinand heating of the resin system during cure thereof enables themorphology of the modified vinyl ester resin composition of the presentinvention to be controlled. More particularly, the modified vinyl esterresin product of the present invention must contain small particles tobe effective in many contemplated end use applications. Small particlesare produced as a result of the physical association or affiliation ofthe additive rubber particles with the rubber particles previouslyreacted into the backbone of the base resin. Such small particles have asize of less than 10,000 angstroms, and preferably less than 1,000angstroms. The presence of small particles allows shear flow and shearyielding to occur in the vinyl ester resin. Thus, unexpectedly goodimprovement in toughness or fracture energy (G_(Ic)) are observed in themodified vinyl ester resin product. It is understood that largeparticles may be present together with such small particles resulting ina bimodal morphological or particle size distribution. However, if toomany large particles are present or if such large particles exceed500,000 angstroms, it is believed that such large particles would serveas flaws in the modified vinyl ester resin product thereby reducing itstoughness. Morphological comparisons are made in FIGS. 5 through 7, withFIGS. 5 and 6 showing vinyl ester resins modified by the prior artmethods of adduction and admixture, respectively, and containing morelarge particles than observed in FIG. 7 which illustrates the modifiedvinyl ester resin composition of the present invention.

The invention will be better understood by reference to the followingexamples which do not serve to limit the invention.

EXAMPLE 7

The recipes set forth below in Table II were prepared in the followingmanner. An epoxy-terminated butadiene-acrylonitrile type copolymeradditive containing 17 percent bound acrylonitrile, which is soldcommercially as a 50 percent solution in styrene by the B. F. GoodrichCompany of Akron, Ohio under the label ETBN X40, was admixed withDerakane 411 vinyl ester base resin in Recipes 2 through 4. Derakane 411is a vinyl ester resin having no rubber content. Cobalt napthenate andmethylethyl ketone peroxide curing agent then were added to the mixturewhich was placed in teflon-coated aluminum molds to a sample thicknessof about 1/4 inch. All recipes were cured for one hour at 60° C. andsubsequently for 2 hours at 120° C. Table II also sets forth the totalrubber content of the modified Derakane 411 system. Mechanicalproperties were measured using ASTM procedure D-638, and fractureenergies were measured using ASTM procedure E-399 using a compacttension specimen. Glass transitions (Tg) were measured using a MetlerDSC instrument.

                  TABLE II                                                        ______________________________________                                                     RECIPES                                                                       1      2       3        4                                        ______________________________________                                        DERAKANE 411   100      100     100    100                                    ETBN X40 (17% bound                                                                          0         10      20     30                                    acrylonitrile)                                                                Cobalt Nap.    0.5      0.5     0.5    0.5                                    MEK Peroxide   2         2       2      2                                     Tot. Rubber    0        4.2     8.3    12.5                                   Content                                                                       PROPERTIES AFTER CURING 1 HR. @ 60° C. +                               2 HRS. @ 120° C.                                                       Ten. Stg., psi 4450     7750    6920   4000                                   Elongation, %  1.28     3.67    4.67   2.30                                   Modulus, GPa   3.10     2.41    1.82   1.730                                  K.sub.Ic, MN/m.sup.3/2                                                                       0.610    1.150   1.24   1.420                                  G.sub.Ic, kJ/m.sup.2                                                                         0.107    0.485    0.742 1.030                                  Tg, °C. 118      121     119    119                                    ______________________________________                                    

The data in Table II shows about a 9 to 10 gold increase in fractureenergy G_(Ic) from the unmodified Derakane 411 resin of recipe 1 whichis free of rubber, to one that contains 12.5 parts per 100 parts of thebase resin rubber content of recipe 4.

EXAMPLE 8

The recipes set forth below in Table III were prepared and tested in thesame manner as the recipes of Table II of Example 7.

                  TABLE III                                                       ______________________________________                                                   RECIPES                                                                       5     6       7       8     9                                      ______________________________________                                        DERAKANE 8084                                                                              100     100     100   100   100                                  ETBN X40      0       5       10    15    20                                  (17% Bound                                                                    Acrylonitrile)                                                                Cobalt Nap.  0.5     0.5     0.5   0.5   0.5                                  MEK Peroxide  2       2       2     2     2                                   Tot. Rubber  7.5     9.6     11.7  13.7  15.8                                 Cont.                                                                         PROPERTIES AFTER CURING 1 HR. @ 60° C. +                               2 HRS. @ 120° C.                                                       Ten. Stg., psi                                                                             6900    7760    6470  6130  4920                                 Elongation, %                                                                              2.03    6.10    3.66  6.81  4.27                                 Modulus, GPa 2.62    2.66    2.08  2.26  1.72                                 K.sub.Ic, MN/m.sup.3/2                                                                     1.13    1.87    1.97  2.12  1.99                                 G.sub.Ic, kJ/m.sup.2                                                                        0.427  1.16    1.65  1.77  2.04                                 Tg, ° C.                                                                            113     114     109   121   113                                  ______________________________________                                    

The data of Table III shows improvements in fracture energy for ETBN RLPadditive admixed with Derakane 8084, which is a vinyl ester resin havingan RLP already reacted into the polymer backbone, over those forDerakane 411 set forth in Table II of Example 7. More particularly,recipes 7 and 8 of Table III contrasted with recipe 4 of Table II eachshow over a 1.5 fold increase in fracture energy for RLP additiveadmixed with Derakane 8084 compared to admixture with Derakane 411, forgenerally similar total rubber contents in the respective vinyl esterresin systems. The data in Table II also shows from about at least atwo-fold increase up to nearly a five-fold increase in fracture energyvalues for the various recipes 6 through 9 of Derakane 8084 having anRLP additive admixed therewith, over recipe 5 for Derakane 8084 havingno RLP additive admixed therewith wherein its total rubber content beingattributed to the RLP reacted into the backbone of the vinyl esterresin. Moreover, the data show that mechanical property retention isalso better for recipes of Derakane 8084 having an ETBN additive ascompared to recipes of Derakane 411 having the same additive at similartotal rubber levels.

EXAMPLE 9

The receipes set forth below in Table IV were prepared and tested in thesame manner as set forth in Example 7 above.

                  TABLE IV                                                        ______________________________________                                                    RECIPES                                                                       10     11      12        13                                       ______________________________________                                        DERAKANE 8084 100      50      50      50                                     DERAKANE 411  0        50      50      50                                     ETBN X40 (17% Bound                                                                         0         9      15      21                                     Acrylonitrile)                                                                Cobalt Nap.   0.5      0.5     0.5     0.5                                    MEK Peroxide  2         2       2       2                                     Tot. Rubber Cont.                                                                           7.5      7.5     10.0    12.5                                   PROPERTIES AFTER CURING 1 HR. & 60° C. +                               2 HRS. @ 120° C.                                                       Ten. Stg., psi                                                                              7175     7190    5800    5090                                   Elongation, % 2.34     6.29    5.11    5.55                                   Modulus, GPa  2.585    1.94    1.76    1.46                                   K.sub.Ic, MN/m.sup.3/2                                                                      1.115    1.46    1.67    1.61                                   G.sub.Ic, kJ/m.sup.2                                                                        0.423     0.969  1.40    1.57                                   Tg, °C.                                                                              113      117     118     118                                    ______________________________________                                    

The data set forth above in Table IV shows that a 50/50 blend ofDerakane 8084 and Derakane 411 containing ETBN X40 additive as shown inrecipe 11 gives at least a twofold increase in fracture energy overDerakane 8084 of receipe 10 which is free of an ETBN X40 additive forsimilar total rubber contents. Moreover, comparing recipes 11 and 13 ofTable IV to recipes 3 and 4 of Table II, respectively, show that a 50/50blend of Derakane 8084 and Derakane 411 containing an RLP additive showabout a 1.3 and about a 1.5 fold increase in fracture energy, forsimilar levels of total rubber content over the Derakane 411 having ETBNX40 admixed therewith. This conclusion is shown graphically in FIG. 1.Moreover, retention of mechanical properties in the Derakane 411/8084blends containing RLP additives is good.

EXAMPLE 10

The recipes set forth below in Table V were prepared and tested in thesame manner as the recipes in Table II of Example 7 above. Anepoxy-terminated butadiene-acrylonitrile type copolymer additivecontaining 26 percent acrylonitrile, was admixed with Derakane 8084 inrecipes 14 and 15 and with Derakane 411 in recipes 16 through 18.

                  TABLE V                                                         ______________________________________                                                   RECIPES                                                                       14    15      16      17    18                                     ______________________________________                                        DERAKANE 8084                                                                              100     100      0     0     0                                   DERAKANE 411  0       0      100   100   100                                  ETBNX13      2.5     7.5     7.5    10    15                                  (26% bound                                                                    acrylonitrile)                                                                Cobalt Nap. (10%)                                                                          0.5     0.5     0.5   0.5   0.5                                  MEK Peroxide  2       2       2     2     2                                   Tot. Rubber  9.6     13.7    6.2   8.2   12.3                                 Cont.                                                                         PROPERTIES AFTER CURING 1 HR. @ 60° C. +                               2 HRS. @ 120° C.                                                       Ten. Stg., psi                                                                             8160    6680    8230  7150  6000                                 Elongation, %                                                                              8.79    5.95    3.51  3.68  3.53                                 Modulus, GPa 2.24    1.91    2.47  2.04  1.92                                 K.sub.Ic, MN/m.sup.3/2                                                                     1.77    2.26    1.31  1.54  1.41                                 G.sub.Ic, kJ/m.sup.2                                                                       1.24    2.36    0.61  1.03  0.91                                 Tg, °C.                                                                             113     112     117   117   119                                  ______________________________________                                    

The mechanical property and fracture energy results for the ETBNadditive utilized in the recipes of Table V above are similar to thoseobserved for ETBN having 17 percent bound acrylonitrile content as setforth in Tables II and III above, thus showing that ETBN containing 26percent bound acrylonitrile gives good results as an RLP additivesimilar to those attained when ETBN containing 17 percent boundacrylonitrile is utilized. FIG. 2 is a plot of the fracture energy datafrom Table V against the total rubber content of the modified resinsystem.

EXAMPLE 11

The recipes set forth below in Table VI were prepared and tested in thesame manner as the recipes in Table II of Example 7. Table VI providesdata for recipes of vinyl ester resins admixed withvinylidene-terminated butadiene-acrylonitrile type copolymer additivecontaining 20 percent bound acrylonitrile, and sold under the labelVTBNX X43 by the B. F. Goodrich Company.

                  TABLE VI                                                        ______________________________________                                                    RECIPE                                                                        19     20      21       22                                        ______________________________________                                        DERAKANE 8084 100      100     0      0                                       DERAKANE 411  0         0      100    100                                     VTBNX X43     5        10      5      10                                      (20% bound                                                                    acrylonitrile)                                                                Styrene       5        10      5      10                                      Cobalt Nap.   0.5      0.5     0.5    0.5                                     MEK Peroxide  2         2      2      2                                       Tot. Rubber Cont.                                                                           12.1     16.6    4.6    9.1                                     PROPERTIES AFTER CURING 1 HR. @ 60° C. +                               2 HRS. @ 120° C.                                                       Ten. Stg., psi                                                                              6550     4310    7310   5970                                    Elongation, % 3.69     6.5     2.33   2.37                                    Modulus, GPa  1.85      1.22   2.23   2.04                                    K.sub.Ic, MN/m.sup.3/2                                                                      1.5      1.4     0.94   1                                       G.sub.Ic, kJ/m.sup.2                                                                        1.08      1.41   0.35   0.43                                    Tg, °C.                                                                              93.6     96.2    120    113                                     ______________________________________                                    

The data of Table VI shows that admixture of VTBNX X43 RLP additive withDerakane 8084 gives tougher cured systems than observed in Derakane 8084alone (see recipes 5 and 10 of Tables III and IV, respectively), or thanobserved in an admixture of VTBNX X43 with Derakane 411. However, theabsolute values of fracture energies are lower for VTBNX X43 (seereceipes 19 and 20) compared with ETBN X40 (containing 17 percent boundacrylonitrile) as shown in recipes 7 and 9 of Table III above forsimilar total rubber content levels. The absolute values of fractureenergies are lower for VTBNX X43 of recipe 19 compared with ETBN XI3containing 26 percent bound acrylonitrile as shown in recipe 15 of TableV above for similar total rubber content levels. FIG. 3 is a plot offracture energies versus the amount of total rubber content for the dataof Table VI, and when compared with FIGS. 1 and 2 shows that thefracture energies for VTBNX X43 additive modified Derakane 8084 arelower than the fracture energies for ETBN X40 and ETBN X13 additivemodified Derakane 8084, respectively.

EXAMPLE 12

The recipes set forth below in Table VII were prepared and tested in thesame manner as the recipes of Table II of Example 7. Ahydroxyl-terminated ephihalohydrin type polymer additive, sold under thelabel Hydrin 10X2 by the B. F. Goodrich Company of Akron, Ohio, wasadmixed with Derakane 8084 and Derakane 411.

                  TABLE VII                                                       ______________________________________                                                  RECIPE                                                                        23    24      25       26    27                                     ______________________________________                                        DERAKANE 8084                                                                             100     100     0       0     0                                   DERAKANE 411                                                                               0       0      100    100   100                                  HYDRIN 10X2 2.5     7.5     5      10    15                                   (no. avg. molec.                                                              wt. = 3300)                                                                   Styrene     2.5     7.5     5      10    15                                   Cobalt Nap. 0.5     0.5     0.5    0.5   0.5                                  MEK Peroxide                                                                               2       2      2       2     2                                   Tot. Rubber Cont.                                                                          10     15      5      10    15                                   PROPERTIES AFTER CURING 1 HR. @ 60° C. +                               2 HRS. @ 120° C.                                                       Ten. Stg., psi                                                                            7980    7610    8880   6620  7130                                 Elongation, %                                                                             2.66    4.41    3.14   2.37  3.14                                 Modulus, GPa                                                                              2.14    1.93    2.02   1.00  1.88                                 K.sub.Ic, MN/m.sup.3/2                                                                    1.33    1.97     0.923  0.894                                                                               0.861                               G.sub.Ic, kJ/M.sup.2                                                                      0.73    1.77    0.37   0.35  0.35                                 Tg, °C.                                                                            114     114     121    120   120                                  ______________________________________                                    

The fracture energy data from Table VII is plotted in FIG. 4. From thedata set forth above in Table VII and the graph in FIG. 4, it isobserved that Hydrin 10X2 additive RLP does not give comparably goodfracture energy values for similar total rubber contents when admixedwith Derakane 8084 as illustrated in recipes 23 and 24, as does ETBN X40additive as shown in recipes 6 and 9 of Table III and FIG. 1, nor doesHydrin 10X2 compare favorably with the fracture energies observed inDerakane 8084 having an ETBN RLP additive containing 26 percent boundacrylonitrile as shown in recipes 14 and 15 of Table V and FIG. 2.

Thus, it can be seen from the data set forth above in the examples andtables that vinyl ester resins modified according to the presentinvention display improved toughness, as measured by fracture energy,over vinyl ester resins modified with RLPs by either of the prior artmethods of adduction or admixing alone. Vinyl ester resins modified inaccordance with the present invention have use in numerous corrosionresistant applications such as pipes and adhesives.

While in accordance with the Patent Statutes, the best mode andpreferred embodiment has been set forth, the scope of the invention isnot limited thereto, but rather by the scope of the attached claims.

What is claimed is:
 1. A toughened cured vinyl ester resin compositioncomprising:a cured admixture of a prereacted vinyl ester base resinhaving a reactive liquid polymer reacted into its backbone; and aneffective amount of a reactive liquid polymer additive to improve thefracture energy of the cured vinyl ester resin composition by an amountgreater than about 1.2 times the base resin.
 2. The composition of claim1, wherein said base resin is the reaction product of an epoxy resin, anunsaturated monocarboxylic acid and the reactive liquid polymer reactedinto the backbone of said base resin; wherein said backbone reactiveliquid polymer is a polyfunctional carboxyl-terminated type polymerhaving a functionality of from about 0.8 to about 3.5; wherein saidadditive reactive liquid polymer is utilized in an amount of from about2 parts to about 30 parts per 100 parts of said base resin; and whereinsaid cured vinyl ester resin composition has a fracture energy ofgreater than about 1.5 times said base resin.
 3. The composition ofclaim 2, wherein said additive reactive liquid polymers arenonfunctional, monofunctional, difunctional, or blends thereof.
 4. Thecomposition of claim 2, wherein said backbone reactive liquid polymer isa statistical difunctional carboxyl-terminated type polymer having afunctionality of from about 1.7 to about 2.4; wherein said additivereactive liquid polymer is utilized in an amount of from about 2 toabout 20 parts per 100 parts of said base resin; and wherein said curedvinyl ester resin composition has a fracture energy of greater thanabout 2 times said base resin.
 5. The composition of claim 4, whereinsaid backbone reactive liquid polymer is a carboxyl-terminated butadienetype polymer having a functionality of about 2; wherein said additivereactive liquid polymer is a polyfunctional carboxyl-terminatedbutadiene type polymer, a polyfunctional carboxyl-terminatedbutadiene-acrylonitrile type random copolymer, a statisticaldifunctional carboxyl-terminated butadiene-acrylonitrile-acrylic acidterpolymer, a polyfunctional epoxy-terminated butadiene-acrylonitriletype copolymer, a statistical difunctional hydroxyl-terminatedepihalohydrin type polymer, or a statistical difunctionalvinylidene-terminated butadiene-acrylonitrile type copolymer; whereinsaid additive reactive liquid polymer is utilized in an amount of fromabout 2 parts to about 10 parts per 100 parts of said base resin; andwherein said cured vinyl ester resin composition has a fracture energyof greater than about 3 times said base resin and a particle size ofless than about 10,000 angstroms.
 6. The composition of claim 4, whereinsaid backbone reactive liquid polymer is a carboxyl-terminatedbutadiene-acrylonitrile type random copolymer having a functionality offrom about 1.8 to about 1.85; wherein said additive reactive liquidpolymer is utilized in an amount of from about 2 parts to about 10 partsper 100 parts of said base resin; wherein said additive reactive liquidpolymer is a polyfunctional carboxyl-terminated butadiene type polymer,a polyfunctional carboxyl-terminated butadiene-acrylonitrile type randomcopolymer, a statistical difunctional carboxyl-terminatedbutadiene-acrylonitrile-acrylic acid terpolymer, a polyfunctionalepoxy-terminated butadiene-acrylonitrile type copolymer, a statisticaldifunctional hydroxyl-terminated epihalohydrin type polymer, or astatistical difunctional vinylidene-terminated butadiene-acrylonitriletype copolymer; wherein said additive reactive liquid polymer isutilized in an amount of from about 2 parts to about 10 parts per 100parts of said base resin; and wherein said cured vinyl ester resincomposition has a fracture energy of greater than about 3 times saidbase resin and a particle size of less than about 10,000 angstroms. 7.The composition of claim 4, wherein said backbone reactive liquidpolymer is a carboxyl-terminated butadiene-acrylonitrile-acrylic acidtype terpolymer having a functionality of about 2.3; wherein saidadditive reactive liquid polymer is a polyfunctional carboxyl-terminatedbutadiene type polymer, a polyfunctional carboxyl-terminatedbutadiene-acrylonitrile type random copolymer, a statisticaldifunctional carboxyl-terminated butadiene-acrylonitrile-acrylic acidterpolymer, a polyfunctional epoxy-terminated butadiene-acrylonitriletype copolymer, a statistical difunctional hydroxyl-terminatedepihalohydrin type polymer, or a statistical difunctionalvinylidene-terminated butadiene-acrylonitrile type copolymer; whereinsaid additive reactive liquid polymer is utilized in an amount of fromabout 2 parts to about 10 parts per 100 parts of said base resin; andwherein said cured vinyl ester resin composition has a fracture energyof greater than about 3 times said base resin and a particle size ofless than about 10,000 angstroms.
 8. The composition of claim 5, whereinsaid additive reactive liquid polymer is a statistical difunctionalepoxy-terminated butadiene-acrylonitrile type copolymer containing 17percent or 26 percent bound acrylonitrile; wherein said cured vinylester resin composition has a fracture energy of greater than about 4times said base resin and a particle size of less than about 1,000angstroms.
 9. The composition of claim 6, wherein said additive reactiveliquid polymer is a statistical difunctional epoxy-terminatedbutadiene-acrylonitrile type copolymer containing 17 percent or 26percent bound acrylonitrile; wherein said cured vinyl ester resincomposition has a fracture energy of greater than about 4 times saidbase resin and a particle size of less than about 1,000 angstroms. 10.The composition of claim 7, wherein said additive reactive liquidpolymer is a statistical difunctional epoxy-terminatedbutadiene-acrylonitrile type copolymer containing 17 percent or 26percent bound acrylonitrile; wherein said cured vinyl ester resincomposition has a fracture energy of greater than about 4 times saidbase resin and a particle size of less than about 1,000 angstroms. 11.The composition of claim 8, wherein said cured vinyl ester resincomposition has a fracture energy of from greater than about 5 times toabout 50 times said base resin.
 12. The composition of claim 9, whereinsaid cured vinyl ester resin composition has a fracture energy of fromgreater than about 5 times to about 50 times said base resin.
 13. Thecomposition of claim 10, wherein said cured vinyl ester resincomposition has a fracture energy of from greater than about 5 times toabout 50 times said base resin.
 14. A vinyl ester resin compositioncomprising:a generally uniformly dispersed admixture of a prereactedvinyl ester base resin having a reactive liquid polymer reacted into itsbackbone; and an effective amount of a reactive liquid polymer additiveto improve the fracture energy of the vinyl ester resin composition. 15.The composition of claim 14, wherein said base resin is the reactionproduct of an epoxy resin, an unsaturated monocarboxylic acid and thereactive liquid polymer reacted into the backbone of said base resin;wherein said backbone reactive liquid polymer is a polyfunctionalcarboxyl-terminated type polymer having a functionality of from about0.8 to about 3.5; wherein said additive reactive liquid polymer isutilized in an amount of from about 2 parts to about 30 parts per 100parts of said base resin; and wherein said cured vinyl ester resincomposition has a fracture energy of greater than about 1.5 times saidbase resin.
 16. The composition of claim 15, wherein said backbonereactive liquid polymer is a statistical difunctionalcarboxyl-terminated type polymer having a functionality of from about1.7 to about 2.4; wherein said additive reactive liquid polymer isutilized in an amount of from about 2 to about 20 parts per 100 parts ofsaid base resin; and wherein said cured vinyl ester resin compositionhas a fracture energy of greater than about 2 times said base resin. 17.The composition of claim 16, wherein said backbone reactive liquidpolymer is a carboxyl-terminated butadiene type polymer having afunctionality of about 2; wherein said additive reactive liquid polymeris a polyfunctional carboxyl-terminated butadiene type polymer, apolyfunctional carboxyl-terminated butadiene-acrylonitrile type randomcopolymer, a statistical difunctional carboxyl-terminatedbutadiene-acrylonitrile-acrylic acid terpolymer, a polyfunctionalepoxy-terminated butadiene-acrylonitrile type copolymer, a statisticaldifunctional hydroxyl-terminated epihalohydrin type polymer, or astatistical difunctional vinylidene-terminated butadiene-acrylonitriletype copolymer; wherein said additive reactive liquid polymer isutilized in an amount of from about 2 parts to about 10 parts per 100parts of said base resin; and wherein said cured vinyl ester resincomposition has a fracture energy of greater than about 3 times saidbase resin and a particle size of less than about 10,000 angstroms. 18.The composition of claim 16, wherein said backbone reactive liquidpolymer is a carboxyl-terminated butadiene-acrylonitrile type randomcopolymer having a functionality of from about 1.8 to about 1.85;wherein said additive reactive liquid polymer is utilized in an amountof from about 2 parts to about 10 parts per 100 parts of said baseresin; wherein said additive reactive liquid polymer is a polyfunctionalcarboxyl-terminated butadiene type polymer, a polyfunctionalcarboxyl-terminated butadiene-acrylonitrile type random copolymer, astatistical difunctional carboxyl-terminatedbutadiene-acrylonitrile-acrylic acid terpolymer, a polyfunctionalepoxy-terminated butadiene-acrylonitrile type copolymer, a statisticaldifunctional hydroxyl-terminated epihalohydrin type polymer, or astatistical difunctional vinylidene-terminated butadiene-acrylonitriletype copolymer; wherein said additive reactive liquid polymer isutilized in an amount of from about 2 parts to about 10 parts per 100parts of said base resin; and wherein said cured vinyl ester resincomposition has a fracture energy of greater than about 3 times saidbase resin and a particle size of less than about 10,000 angstroms. 19.The composition of claim 16, wherein said backbone reactive liquidpolymer is a carboxyl-terminated butadiene-acrylonitrile-acrylic acidtype terpolymer having a functionality of about 2.3; wherein saidadditive reactive liquid polymer is a polyfunctional carboxyl-terminatedbutadiene type polymer, a polyfunctional carboxyl-terminatedbutadiene-acrylonitrile type random copolymer, a statisticaldifunctional carboxyl-terminated butadiene-acrylonitrile-acrylic acidterpolymer, a polyfunctional epoxy-terminated butadiene-acrylonitriletype copolymer, a statistical difunctional hydroxyl-terminatedepihalohydrin type polymer, or a statistical difunctionalvinylidene-terminated butadiene-acrylonitrile type copolymer; whereinsaid additive reactive liquid polymer is utilized in an amount of fromabout 2 parts to about 10 parts per 100 parts of said base resin; andwherein said cured vinyl ester resin composition has a fracture energyof greater than about 3 times said base resin and a particle size ofless than about 10,000 angstroms.
 20. The composition of claim 17,wherein said additive reactive liquid polymer is a statisticaldifunctional epoxy-terminated butadiene-acrylonitrile type copolymercontaining 17 percent or 26 percent bound acrylonitrile; wherein saidcured vinyl ester resin composition has a fracture energy of greaterthan about 4 times said base resin and a particle size of less thanabout 1,000 angstroms.
 21. The composition of claim 18, wherein saidadditive reactive liquid polymer is a statistical difunctionalepoxy-terminated butadiene-acrylonitrile type copolymer containing 17percent or 26 percent bound acrylonitrile; wherein said cured vinylester resin composition has a fracture energy of greater than about 4times said base resin and a particle size of less than about 1,000angstroms.
 22. The composition of claim 19, wherein said additivereactive liquid polymer is a statistical difunctional epoxy-terminatedbutadiene-acrylonitrile type copolymer containing 17 percent or 26percent bound acrylonitrile; wherein said cured vinyl ester resincomposition has a fracture energy of greater than about 4 times saidbase resin and a particle size of less than about 1,000 angstroms. 23.The composition of claim 20, wherein said cured vinyl ester resincomposition has a fracture energy of from greater than about 5 times toabout 50 times said base resin.
 24. The composition of claim 21, whereinsaid cured vinyl ester resin composition has a fracture energy of fromgreater than about 5 times to about 50 times said base resin.
 25. Thecomposition of claim 22, wherein said cured vinyl ester resincomposition has a fracture energy of from greater than about 5 times toabout 50 times said base resin.